MOBILIZATION OF ANNEXIN-V DURING THE UPTAKE OF DNP-ALBUMIN BY HUMAN DENDRITIC CELLS

Dendritic cells play a crucial role in antigen presentation in various tissues. The endocytic capacity of these cells has been regarded as m inimal, but recent work on dendritic cells from mouse spleen has discl osed that the fluid-phase traffic through late endosomes is as active in dendritic cells as in other antigen-presenting cell types. We show that cultured human dendritic cells express the annexins I, III, IV, V and VI, as detected by immunofluorescence staining. The annexins are cytosolic Ca2+-dependent proteins with the ability to promote vesicle aggregation and membrane fusion through their capacity to bind to memb rane phospholipids. Annexin I and VI appeared to outline the cytoskele ton and the plasma membrane in cultured human dendritic cells. Studies using confocal laser scanning microscopy showed that during the endoc ytosis of fluorescent dinitrophenyl-conjugated albumin by dendritic ce lls, there was a redistribution of annexin V which was found to coloca lize with vesicles containing dinitrophenyl-FITC-conjugated albumin.